1. Field of the Invention
The present invention relates to a solid state imaging device that is applied to, for example, an electronic endoscope or the like. More particularly, it is to realize miniaturization of a solid state imaging unit by constituting it in that a projection area of a solid state imaging chip comprising a CCD, not packaged, can accommodate a circuit board, the electronic parts to be mounted thereon, and a signal cable connected to a terminal, thereby to decrease the outer diameter and length of the end portion of an electronic endoscope or the like.
2. Description of the Related Art
Recently, various kinds of electronic endoscopes using a solid state imaging chip with a charged coupled device (CCD) or the like as an imaging means have been proposed, and this solid state imaging chip is embedded in a rigid end portion of a tube of the endoscope to be inserted into a body. Therefore, it is preferable that the diameter and length of the end portion of the tube is lessened as much as possible in order to relieve a patient's pain. Accordingly, how much degree the solid state imaging chip can be miniaturized is a very important technical theme.
An endoscope using the conventional solid state imaging chip is disclosed in, for example, the Patent Publication No. 2607542 (Japanese Patent Publication Laid-Open No. 63-313970) and an example of the structure of this endoscope is shown in FIG. 1. Electronic parts 61 and 62 are mounted on one surface (upper surface) and the other surface (lower surface) of a circuit board, indicated by the reference numeral 60, which is horizontally disposed. A solid state imaging chip 63 that is not packaged with the electronic parts 61 is coupled to one end portion of the circuit board 60 in an orthogonal direction. The circuit board 60 and the solid state imaging chip 63 are electrically connected to each bonding pad, not illustrated, that is provided in the end surface of the circuit board 60 and in the front surface of the solid state imaging chip 63, by a bonding wire 64. Signal cables 65 are connected to the other end portion of the circuit board 60.
The front portion of the solid state imaging chip 63 is sealed and covered with a cover glass 66, and optical lenses 68, 69, and 70 supported by a cylindrical mirror 67 in accordance with an optical axis of the solid state imaging chip 63 are disposed in the front of the cover glass 66. The above-mentioned components are respectively covered with a sheath 71, and a space within the sheath 71 is charged with a molding material 72.
As another example, there is an endoscope disclosed in, for example, the Japanese Patent Publication Laid-Open No. 63-290541. In the endoscope, a metal plate with the solid state imaging chip bonded thereto, a circuit board with electronic parts mounted thereon, and a base connecting the circuit board to a signal cable are disposed in parallel, and these elements are electrically connected by a cylindrical flexible board around their peripheral portion.
The endoscope disclosed in the Patent Publication No. 2607542, however, needs a bonding space in the outer circumferential portion around the solid state imaging chip 63, because of adopting a method of connecting one end of the circuit board 60 to the solid state imaging chip 63 by the bonding wire 64, and the outer diameter of the end portion of the endoscope necessarily becomes larger for the space, which has been an impediment to reducing the diameter at the end portion of the endoscope. Further, since the signal cable 65 is connected to the other end of the circuit board 60 on the surface with the electronic parts 61 mounted thereon, the circuit board 60 needs the length more for the connection, which has been an impediment to shortening the length at the rigid end portion of the endoscope.
While, in the endoscope disclosed in the Japanese Patent Publication Laid-Open No. 63-290541, the solid state imaging device needs a space for bonding and electrically connecting the solid state imaging chip, metal plate, circuit board, and base in the longitudinal direction of the rigid end portion of the endoscope, and therefore the rigid end portion of the endoscope cannot help getting longer for the space. Since the outer peripheral portion around the solid state imaging chip, metal plate, circuit board, and base is surrounded by a cylindrical flexible board to connect them electrically, the diameter of the rigid end portion of the endoscope cannot help getting larger. Accordingly, it is impossible to further decrease the rigid end portion of the endoscope in diameter and length.
In order to solve the above-mentioned problems, the object of the present invention is to miniaturize an imaging unit, thereby to obtain a solid state imaging device capable of further decreasing the rigid end portion of an endoscope in diameter and length.